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Darwin Correspondence Project

To W. E. Darwin   22 June [1866]1

Down

June 22nd.

Dear William—

I have forwarded the business letters.2

If your case turns out true (wh. it probably won’t) it will be a most interesting discovery & I vow you shall write a paper & publish it; but it must be well worked out first.3 I presume the case is as follows; let us take a long & short-styled primrose and suppose the female organs to abort in both & then we shd have two males; & now take another pair & abort the male organs in both & we shd. have two females; & the case wd be like that of the Rhamnus. In all my speculations I never dreamed of such a case. Now the great thing is to be sure that the pollen grains differ in size in the two males. I have more confidence in measuring a few choice grains with the micrometer than with the camera.4 You say that the grains are largest in what you call the pistillate males i.e. what primordially must have been the long-styled forms. Now it is a universal law in the most different orders, as in Primula Hottonia, Mitchella, Pulmonaria, Menyanthes, Sethia, Lythrum, and Oxalis that the pollen grains from the longer stamens in the short styled form are the largest; & this is unfortunately against yr. view.5 But as the pollen is equal in the two forms of Linum there may be some way of wriggling out of this difficulty.6

Is there any difference in length in the stamens of the two male forms? Are you pretty sure that the two male forms do not graduate into each other; & so with the two female forms? It wd be eminently well to ascertain whether yr. pistillate male sets a few berries. I could detect no difference in length in the rudimentary stamens of the two females. If you are sure about the difference in size in the pollen of the two males, the case must be extraordinary whether or no we can understand it. If you have marked all four forms I would get you in the autumn when the leaves are shedding, to cut me off some branches & I daresay we could make them strike & then I could experimentise on them; I suppose the bushes would be two big to dig up? I could give you the results of any experiments for your paper but this is looking a long way ahead.7

Do not be discouraged if the whole case blows up— I am well accustomed to such explosions.

yr affectate Father | Ch. Darwin (miserable forgery)8 | Ch. Darwin

It wd be well to look at ovules in pistillate male:—9 Asa Gray says in letter that Rhamnus lanceolatus of U. States, has 2 forms, which differ only in pistils— The long-styled is much the most fruitful, but the short-styled does bear some fruit.— He adds that the stamens in the 2 forms were not rigorously compared.—10

Footnotes

The year is established by the relationship between this letter and the letter from W. E. Darwin, 20 June [1866].
With his letter of 20 June [1866], William had sent some orders for dividends to be signed and forwarded to CD’s brother, Erasmus Alvey Darwin.
William had observed four flower forms, two male and two female, in Rhamnus cathartica, and believed that the plant had once been dimorphic. See letters from W. E. Darwin, 20 June [1866] and 21 June [1866].
William frequently measured the sizes of pollen-grains with the aid of a camera lucida (see, for example, letter from W. E. Darwin, 8 May [1866] and n. 2).
See letter from W. E. Darwin, 20 June [1866] and n. 5. CD discussed each of these genera in Forms of flowers.
Although Linum species are heterostyled, CD had found that the pollen-grains of the two forms, unlike other heterostyled genera that he had observed, were indistinguishable under the microscope (‘Two forms in species of Linum’, p. 75; Collected papers 2: 98).
The account of Rhamnus cathartica was not published until 1877 in Forms of flowers (pp. 293–5). CD credited William with many of the observations, and added that he could ‘form no satisfactory theory how the four forms … originated’ (p. 295).
The letter down to, and including, the first signature is in Henrietta Emma Darwin’s hand; the remainder is in CD’s hand.
See CD’s annotations to the letter from W. E. Darwin, [18 June 1866] and n. 3.
Asa Gray had described two hermaphrodite forms of Rhamnus lanceolatus in his letter of 11 October 1861 (Correspondence vol. 9), noting that the long-styled form was more fruitful. However, in Forms of flowers, pp. 295–6, CD reported on Gray’s authority that the short-styled form was more fruitful.

Summary

Polymorphism in Rhamnus.

Letter details

Letter no.
DCP-LETT-5131
From
Charles Robert Darwin
To
William Erasmus Darwin
Sent from
Down
Source of text
DAR 185: 15
Physical description
( A ) 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 5131,” accessed on 18 October 2017, http://www.darwinproject.ac.uk/DCP-LETT-5131

Also published in The Correspondence of Charles Darwin, vol. 14

letter